The invention relates to a network scheduling protocol for transporting data packets. More particularly, this invention relates to a network system and scheduling protocol for transporting variable bit-rate data over a contention and reservation based cable network.
Data over cable system interface specifications (DOCSIS), defines a Media Access Control (MAC) standard for transmitting packetized data over the Internet, through a two-way cable network. Details of the DOCSIS standard can be found in (DOCSIS v1.0) Radio Frequency Specification. In DOCSIS, the cable modem termination system (CMTS) at the cable headend and the cable modems (CMs) at the customer premises constitute a point to multi-point communication network. The CMTS and the corresponding CMs act as forwarding agents that carry packetized data over the Internet transparently. DOCSIS architecture provides a simple and efficient way to carry Internet Protocol (IP) data traffic over a bi-directional cable data network.
Emerging multimedia applications exercise ever increasing demand for service guarantees from cable data networks. These applications include voice over IP (VoIP) for IP telephony service and compressed video over IP for video on demand, video conferencing, and image editing, to name a few. In particular, video encoded according to the Moving Picture Experts Group (MPEG) standard, a widely accepted standard for digital video transmission and storage, has found wide applicability in satellite, cable, and wireless-based video distribution systems, as well as in computer imaging. However, due to the nature of the video bursts and variable bit-rate (VBR) of the MPEG video, reliable transport of MPEG video of exceptional quality over IP networks has become increasingly difficult.
Accordingly, there is a need for a novel quality of service (QoS) scheduling mechanism suitable for transporting variable bit-rate video over a (data over cable system interface specification) DOCSIS compliant cable for improving bandwidth utilization and latency distribution.